The present invention relates to absorbent structures useful in absorbent articles such as diapers, incontinent briefs, training pants, diaper holders and liners, sanitary hygiene garments, and the like. More particularly, the invention relates to absorbent structures that provide articles having improved fit and comfort when dry and particularly when wetted with bodily fluids.
Infants and other incontinent individuals wear absorbent articles such as diapers to absorb and retain urine and other body exudates. Absorbent articles function both to contain the discharged materials and to isolate these materials from the body of the wearer and from the wearer""s garments and bed clothing. Disposable absorbent articles having many different basic designs are known in the art. For example, U.S. Pat. No. Re. 26,152, entitled xe2x80x9cDisposable Diaperxe2x80x9d issued to Duncan and Baker on Jan. 31, 1967, describes a disposable diaper which has achieved wide acceptance and commercial success. U.S. Pat. No. 3,860,003, entitled xe2x80x9cContractable Side Portions For Disposable Diaperxe2x80x9d, issued to Buell on Jan. 14, 1975, describes an elastic leg cuff disposable diaper which has achieved wide acceptance and commercial success.
Many diaper designs are relatively wide and bulky, when dry and particularly when wet, in the region of the article that fits between the legs of the wearer. This results in a certain level of discomfort to the wearer, as these diapers tend to bunch when worn. In an effort to address wearer discomfort, U.S. Pat. No. 4,610,678 (Weisman et al.) describes diapers comprising densified cores that are thinner in this region than were prior designs. Nonetheless, even these articles store significant levels of absorbed fluids in the discharge region of the article. This discharge region is positioned within the portion of the article that fits in the wearer""s crotch region when worn.
Since prior absorbent articles do not effectively distribute fluid, these articles are typically designed to store significant quantities of fluid in the crotch region of the diaper. Thus, upon each loading, this region of the article becomes increasingly bulky and therefore tends to be more uncomfortable for the wearer. See, for example, U.S. Pat. No. 5,098,423 to Pieniak et al., which builds on the disclosure of the Weisman patent, and describes a low dry bulk disposable diaper. The focus of the ""423 patent is an article having a relatively low cross sectional area, when dry, particularly in the xe2x80x9cimpact zonexe2x80x9d (defined in the patent as the second and third fifths of the article""s length). Indeed, an important aspect of the described articles is the ability of the absorbent material in the impact zone to absorb fluid. The patent specifically indicates that at least 60% of the total absorbed fluid is retained in the diaper""s impact zone. Thus, while the patent discusses the desire for improved fit when dry, it fails to address the issue of providing improved fit and comfort throughout the entire wearing period. Moreover, the primary consideration for improving fit is on thin and wide structures which fold and bunch during use, without optimizing narrowness and bulk, dry and wet, of the absorbent material in the crotch region. Accordingly, the articles described in the ""423 patent have in the crotch region an overall low cross sectional area when dry, accomplished by providing a relatively thin (i.e., in the article""s the z-dimension), relatively wide (i.e., in the article""s x-dimension) core. However, the core retains 60% of its absorbent capacity in the crotch region. This results in excess bulk, thickness, thereby reducing the comfort and fit when the article is wetted with body fluid.
Several attempts have been made to provide articles, such as diapers, with increased storage capacity outside of the crotch region. U.S. Pat. No. 4,994,037 (Bernardin, et al.) discloses diapers with absorbent core designs comprising superabsorbent material located in either one or both waist regions of the absorbent core. The structures described therein show low efficiencies of the material usage in the waist regions of the article, because of substantially higher capacity in the crotch region than in either of the waist regions. Although it is pointed out in U.S. Pat. No. 4,994,037, that the superabsorbent material does absorb some liquid, it is not recognized therein that the liquid pick up further away form of the loading area is still significantly reduced. In addition, the reference describes the use of fluff components, especially around the loading region, which thus inevitably will result in a high rewetting tendency of the article.
It therefore would be advantageous to provide an absorbent structure that provides better fit and wearer comfort, even after the structure is wetted with body fluids. It would be further advantageous to provide an absorbent structure which has reduced bulk in the crotch region in both the dry and wet states. Such structures would provide absorbent articles having improved fit and comfort, even when wetted with body fluids.
Therefore, it is an object of the present invention to provide an absorbent structure having improved fit on the wearer during use by reducing the structure""s crotch width dry as well as when the structure is wetted with fluid.
It is a further object of the present invention to provide an absorbent structure that provides reduced caliper in the crotch region of the product when dry as well as when wet which in turn positively impacts comfort and fit.
It is a further object of the present invention to provide an absorbent structure that provides improved comfort for the wearer resulting from the structure""s ability to readily acquire, distribute and store a significant amount of fluid remote from the crotch region of the structure.
It is a further object of the present invention to provide absorbent articles which have low rewet values, thereby providing improved skin dryness.
It is a further object of the present invention to provide articles that more effectively distribute body exudates such that higher absorbent capacities can be achieved even against gravitational forces.
It is a further object of the invention to provide absorbent articles comprising these absorbent structures.
These and other objects of the present invention will be more readily apparent when considered in reference to the following description and when taken in conjunction with the accompanying drawings.
The present invention provides absorbent structures for inclusion in absorbent articles such as diapers, incontinent briefs, training pants, diaper holders and liners, feminine hygiene garments, and the like, designed to provide improved fit and comfort for the wearer while adequately containing body exudates. Such an absorbent article has a containment assembly (chassis) typically comprising a liquid pervious topsheet and a substantially liquid impervious backsheet, and an absorbent core associated with the outer covering layer. The absorbent core is designed so as to be relatively narrow and thin in the crotch region of the diaper, even when the core absorbs significant amounts of fluid during use. To achieve this, the absorbent core is designed such that fluid is moved substantially from the crotch region to the front and/or rear waist regions of the article.
Thus, the absorbent article has an absorbent capacity as determined by the Whole Article Vertical Wicking test, wherein capacities are determined for segments of the article positioned in vertical distance away from the folding line of the article, and wherein the absorbent capacity for a segment at 13.5 cm is at least 0.5 times the capacity for the segment at 0 cm, preferably at least 0.75 times, more preferably 1.25, and most preferably at least two times.
Suitable absorbent articles can also be described by respective calipers at the crotch, namely by the Saturated Crotch Caliper (SCC), and the Actual Wet Crotch Caliper (AWCC), which are determined following the Curved Acquisition test method, whereby the Actual Wet Crotch Caliper is less than the Saturated Crotch Caliper, whilst the article provides a good rewet performance by exhibiting a Post Curved Acquisition Rewet Value of less than about 180 mg.
A suitable absorbent article can also be described by comprising an absorbent core, which has a crotch region and one or more waist regions, whereby the article and the core have a characteristic crotch point and characteristic waist points positioned just outside of the crotch regions, whereby the Actual Wet Crotch Caliper as determined following the Curved Acquisition test method at the crotch point, is less than the Actual Wet Waist Caliper, as determined following the Curved Acquisition test method at a waist point, and the article provides for a good rewet performance by exhibiting a Post Curved Acquisition Rewet Value of less than about 180 mg.
A preferred embodiment of the article according to the present invention comprises an absorbent core with a crotch region and one or more waist regions, which core comprises an acquisition region, a distribution region, a storage region, and a storage/rewet barrier means, which is positioned on the surface of said storage region, which is oriented towards the wearer during use, and which comprises absorbent gelling material.
Preferably, the absorbent article has an Actual Wet Crotch Caliper (AWCC) of less than about 20 mm, preferably less than 15 mm, more preferably less than 10 mm, most preferably less than 5 mm. The absorbent article can have an AWCC of less than 90% of the article""s SCC, preferably less than 50%, more preferably less than 25%. The crotch width of absorbent articles according to the present invention is preferably less than about 90 mm, preferably less than 70 mm, more preferably less than 50 mm. Preferably, the article according to the present invention Dry Crotch Caliper of less than 8 mm preferably less than 5 mm, more preferably less than 3 mm.
When submitting the articles according to the present invention the Curved Acquisition test, they exhibit an initial acquisition rate of at least 5 ml/usec, preferably of at least 10 ml/sec, more preferably greater than 15 ml/sec, or a 4th gush acquisition rate of at least 0.25 mi/sec, preferably at least 0.50 ml/sec, more preferably at least 1.0 ml/sec.
When submitting articles according to the present invention the Post Curved Acquisition Collagen Rewet test, they preferably exhibit a value of less than 150 mg, more preferably less than 100 mg, even more preferably less than 50 mg. For articles comprising a rewet barrier, the Post Curved Acquisition Collagen Rewet is preferably less than the Post Curved Acquisition Collagen Rewet of the absorbent article wherein said rewet barrier region is removed. Preferred materials for the rewet barrier are superabsorbent gelling materials, hydrogels, or superabsorbents; polymeric foam material; HIPE based foams, or combinations thereof.
Absorbent articles according to the present invention can comprise an acquisition region which preferably comprises a material, which has a Medium Desorption Pressure (MDP) value corresponding to a height of less than 15 cm, preferably less than 12 cm, more preferably less than 10 cm, but preferably of more than 5 cm.
In a preferred embodiment, the absorbent core of an absorbent article comprises a liquid acquisition region, a liquid distribution region, and a liquid storage region, whereby at least a portion of the storage region is positioned between the distribution region and the wearer oriented surface of the article during use. The storage region can comprise two separated subregions positioned longitudinally offset from each other. Preferably, the crotch region of the absorbent article has an ultimate storage capacity of less than about 40% of the total ultimate storage capacity of the absorbent core, preferably less than 25%, more preferably less than 10%.
A further preferred article according to the present invention comprises a moisture vapor permeable backsheet. Such an article can comprise an absorbent core which covers a surface area that is less than 60% of the surface area of the moisture vapor permeable backsheet in the crotch region, preferably less than 50%, more preferably less than 25%. The moisture vapor permeable backsheet can comprise microporous films or laminates, nonwovens, monolithic films or combinations thereof, such as laminates.
Absorbent article according to the present invention can comprise distribution material having a liquid flux at 12.4 cm of more than 0.075 g/cm2/sec, preferably more than 0.1 g/cm2/sec, more preferably more than 0.15 g/cm2/sec), when measured according to the Distribution Material Vertical Wicking test, or which have a time to wick to 12.4 cm of less than 300 sec. preferably less than 100 sec, more preferably more than 50 sec when measured according to this test.
Absorbent articles according to the present invention comprise a liquid distribution material having a Capillary sorption desorption height at 90% of desorbed capacity of at least 40 cm. Such materials can be fibrous or foamed liquid distribution materials.
Absorbent articles according to the present invention can comprise an ultimate storage material in the absorbent core, which satisfies at least one of the following requirements of
(a) a Capillary Sorption Absorption Capacity at 35 cm (CSAC 35) of at least 15 g/g; and/or
(b) a Capillary Sorption Absorption Capacity at 0 cm (CSAC 0) of at least 15 g/g and a Capillary Sorption Absorption Efficiency at 40 cm (CSAE 40) of at least 55%; and/or
(c) a Capillary Sorption Absorption Height at 50% of its capacity at 0 cm absorption height (CSAH 50) of at least 35 cm.
A preferable ultimate storage material can comprise a polymeric foam material, preferably derived from high internal phase water-in-oil emulsions, a high surface area fibers, a hydrogel forming materials, or combinations thereof.
Articles according to the present invention preferably further comprise a feces management means positioned between the topsheet of the article, which is oriented towards the wearer during its intended use and the backsheet positioned opposed to the topsheet, providing for a trans-topsheet capacity of at least 0.2 grams per square inch. Preferably, the feces management means is a fibrous web, or a web comprising a backing and a sheet of fibers, which has anchor portions in the backing at spaced bonding locations and has arcuate portions of the sheet projecting from said backing between bonding locations, or an apertured formed film.
The topsheet of the article can be an apertured structure, having a liquid pervious structured carrier with an inner surface oriented towards the interior of the article and an outer surface oriented toward the skin of the wearer when the article is worn, whereby the structured carrier has an effective open area of at least about 12 percent and a plurality of apertures with an effective size greater than 0.1 square millimeters. Optionally, the outer surface of the structured carrier comprises an effective amount of a skin care composition which is semi-solid or solid at 20xc2x0 C. and which is partially transferable to the wearer""s skin.